A transmitter optical subassembly (TOSA) is an important component of an optoelectronic transmitter or transceiver. A typical TOSA includes a semiconductor laser, a lens and a receptacle into which an optical fiber can be inserted easily. The lens, which is for converging light beams to the end of the optical fiber, generally needs to be a small aberration-free lens with high numerical aperture. Small aberration-free lenses with high numerical aperture are difficult to fabricate and costly. Sometimes, they have to be made of sapphire and constitute a significant portion of the manufacturing cost of optoelectronic transmitters and tranceivers.
In a typical optoelectronic transmitter or transceiver, the semiconductor laser emits light beams that have a substantially Gaussian intensity distribution, sometimes called a Gaussian profile. Such light beams, however, suffer significant intermodal dispersion. Thus, they cannot be transmitted for very long distances in multimode fibers.
Accordingly, there exists a need for an inexpensive means for optically coupling a semiconductor laser to an optical fiber. There also exists a need for a means for optically coupling a semiconductor laser to a multimode optical fiber.